SAN DIEGO >> After questioning him, federal agents told the college student swept up in a drug raid to hang tight in the holding cell while they finished the paperwork to release him.

Daniel Chong grew annoyed as he waited hours for them to return. He was livid after spending the night there. He screamed and kicked the door.

Then as the days dragged on, the terrifying realization set in that he was trapped. He had been forgotten in a 5-by-10-foot windowless room, hearing only the muffled sounds of voices and toilets flushing in the Drug Enforcement Administration facility in San Diego.

On the third day, he began to hallucinate. He urinated on a metal bench to be able to drink his urine. He stacked a blanket, his pants and shoes on the bench and tried to reach an overhead fire sprinkler, futilely swatting at it with his cuffed hands to set it off.

Then, the 23-year-old says he gave up and accepted death. He bit into his eyeglasses to break them. He says he used a shard of glass to carve "Sorry Mom" onto his arm so he could leave something for her.

He managed to finish an "S." He says he considered ending his life with the glass to quicken his death.

"I pretty much lost my mind," he told The Associated Press on Wednesday.

Help came after four days, when agents on a fluke opened the door and found him covered in his own feces. He says a bewildered agent asked: "Where’d you come from?"

Chong spent five days in the hospital for dehydration, kidney failure, cramps and a perforated esophagus. He had lost 15 pounds.

His attorneys filed a $20 million claim on Wednesday against the federal agency, saying his treatment constitutes torture under U.S. and international law. The five-page notice, a required precursor to a lawsuit, was sent to the DEA’s chief counsel in Washington, D.C. The $20 million figure refers to the maximum amount that Chong and his lawyers would seek.

The top DEA agent in San Diego, William R. Sherman, said in a statement that he was "deeply troubled" by what happened to Chong and has personally ordered an extensive review of his office’s policies and procedures. The agency declined to say what those were.

Chong was not going to be charged with a crime and should have been released, said a law enforcement official who was briefed on the DEA case and spoke on the condition of anonymity because he wasn’t authorized to speak about the ongoing investigation.

Chong said he has no criminal record.

The incident was one of the worst cases of its kind, said Thomas Beauclair, deputy director of the National Corrections Institute, a federal agency that provides training and technical assistance to corrections agencies.

"That is pretty much unheard of," he said, noting that, in his 40-year career, he has heard of instances where people were forgotten overnight but not for days.

A federal law enforcement official familiar with DEA operations said the agency’s protocols require that cells be checked each night.

The official, who spoke on condition of anonymity because he was not authorized to discuss the matter, said the cell where Chong was held is not intended for overnight stays because it does not have a toilet.

Federal lawmakers are demanding a thorough investigation. U.S. Sen. Barbara Boxer, D-Calif., sent a letter Wednesday to Attorney General Eric Holder.

"Please provide me with the results and the actions the department will take to make sure those responsible are held accountable and that no one in DEA custody will ever again be forced to endure such treatment," the letter stated.

Chong said no one has contacted him personally to apologize.

Chong told the AP his ordeal started after he went to his friend’s house on April 20 to get high, part of a national, annual countercultural ritual on that date. Chong slept there that night and, the next morning, agents stormed into the house. The raid netted 18,000 ecstasy pills, other drugs and weapons. Nine people, including Chong, were taken into custody, according to the DEA.

Chong was questioned, then agents told him he was not a suspect and would be released shortly.

At one point, he ripped a piece of his jacket off with his teeth and shoved it under the door, hoping someone would spot it and free him.

Chong said he ingested a white powder that he found in the cell. Agents later identified it as methamphetamine. Chong said he ingested it to survive.

The next day, hallucinations started, he said. They included Japanese animation characters who told him to dig into the walls to search for water, which he tried, tearing apart the wall’s plastic lining.

People can die from dehydration in as little as three to seven days, said Dr. Wally Ghurabi at UCLA Medical Center in Santa Monica.

Ghurabi said Chong was wise to drink his own urine to stay hydrated.

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Associated Press writers Alicia A. Caldwell and Kevin Freking in Washington, D.C., Elliot Spagat in San Diego, and Amy Taxin in Orange County, Calif., contributed to this report.